GB2044487A

GB2044487A - Fuel injection pump

Info

Publication number: GB2044487A
Application number: GB8007597A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-03-10
Filing date: 1980-03-06
Publication date: 1980-10-15
Also published as: JPS55123353A; GB2044487B; DE2909537A1; US4409942A

Description

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GB 2 044487A 1

SPECIFICATION

A fuel injection pump for an internal combustion engine

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The invention relates to a fuel injection pump for an internal combustion engine comprising a hydraulic speed governor in which an adjusting piston controlling an injection quantity 10 adjusting member is actuated against a spring force by the speed dependent fuel pressure of a pressure source supplied by a fuel feed pump driven in synchronism with the engine.

In a known fuel injection pump having a 1 5 hydraulic governor of this kind, a throttle is arranged between the pressure source and the adjusting piston and effects a certain pressure drop, and the pressure at the rear end of the adjusting piston is controlled by a valve which 20 is acted upon, and controlled by, pressure. A solenoid valve acts as a servo motor by means of which the spaces at both sides of the throttle are interconnectible, the quantity of fuel injected being increased after the spaces 25 have been interconnected. The purpose of this is to increase the engine speed with the same position of the adjusting lever, that is to say, with the same position of the accelerator pedal, although a low gear has been engaged, 30 thus to obtain a higher torque when, for example, travelling uphill or when moving off, that is to say, when a low gear is engaged. Thus, the pressure acting upon the, adjusting piston is increased for the purpose of increas-35 ing the engine speed. This known governor is of extremely complicated construction and its hydraulic control is difficult to survey and control. In addition to this, there is the risk, particularly in the event of jamming of any of 40 the slide valves, that the quantity of fuel injected will be additionally increased upon increasing engine speed and thus increasing hydraulic pressure, which can very rapidly lead to racing of the internal combustion 45 engine.

According to the present invention there is provided a fuel injection pump for an internal combustion engine having a hydraulic speed governor in which an adjusting piston acting 50 upon an injection quantity adjusting member is actuated against spring means by a control pressure of a pressure source supplied at a speed dependent pressure by a feed pump driven at a speed in synchronism with the 55 engine speed, the control pressure being adjustable by means of a valve to effect a change in the injection quantity, the valve being disposed in a passage branching from the pressure source and being controllable by 60 a servo motor, such that the valve is open when the internal combustion engine is cold to lower the control pressure and thereby increase the quantity of fuel injected and the valve is closed when the engine is hot. 65 In contrast to the prior art, the fuel injection pump in accordance with the invention has the advantage of a small regulating unit having a very precise quality of regulation. Moreover, owing to the principle of construction, it 70 is possible to reduce the regulating pressure and thus to increase the engine speed for a specific position of the adjusting lever by allowing a portion of the fuel to flow off. Although the engine speed is increased by 75 opening, the passage, this is only achieved with a shift of the entire level of regulation. As soon as the engine speed increases, the pressure also increases and the engine speed is correspondingly governed down. Thus the in-80 ternal combustion engine does not race as a result of opening a passage.

The present invention will now be described further, by way of example only, with reference to the accompanying drawings, in 85 which:—

Figure 7 is a simplified, longitudinal section through the first embodiment of a fuel injection pump in accordance with the invention; Figure 2 shows a device for adjusting the 90 idling fuel delivery quantity, controlled by a magnet, and

Figure 3 shows the construction of a second embodiment in which the idling fuel delivery adjustment is combined with cold-95 starting advance by the injection timer.

A fuel injection pump in accordance with the invention is illustrated in a greatly simplified form in Fig. 1. A pump piston 2 operates in a housing 1 of the fuel injection pump and 100 is reciprocated and simultaneously rotated by a cam drive (not illustrated). A pump working chamber 3 is defined in the housing 1 by the pump piston 2 and is connected by way of an inlet passage 4 to the pump suction chamber 105 5 disposed in the housing 1. The pump piston 2 incorporates a pressure passage 6 which opens into the pump working chamber 3 and from which a distributor bore 7 branches. The pressure passage 6 is controlled by an annular 110 valve slide 8 acting as a fuel quantity control member. The distributor bore 7 cooperates with pressure conduits 9 which are usually uniformly distributed around the pump piston and each of which incorporates a non-return 115 valve 10. During the suction stroke of the pump, fuel flows from the suction chamber 5 into the pump working chamber 3 by way of the inlet passage 4. During the subsequent pumping stroke of the pump piston 2, and 120 after the inlet passage 4 has closed, fuel under high pressure is conducted by way of the distributor bore 7 to one of the pressure conduits 9 and then, by way of the said pressure conduit and a fuel injection valve 125 (not illustrated) flows into a cylinder of the internal combustion engine to be supplied with fuel. After a corresponding pumping stroke has been covered, in order to terminate the injection operation, the pressure passage 130 6 in the pump piston 2 is opened by the

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annular valve slide 8 by virtue of a mouth of the pressure passage 6 emerging from the annular valve slide 8 during the movement of the pumping stroke.

5 Thus, the quantity of fuel injected depends upon the position of the annular valve slide 8 which is adjustable by means of an hydraulic governer 13 by way of a governor lever 12 pivoted at 11. The hydraulic governor oper-10 ates with an adjusting piston 14, one end face of which is acted upon by the fuel from the suction chamber 5, the operation of the adjusting piston being opposed by a spring unit 1 5 which is arranged on the piston and 1 5 whose forces are arbitrarily variable. The suction chamber 5 receives fuel from a feed pump 16 which is driven at a pump-synchro-nous speed (generally integrated in the pump), the pressure in the suction chamber 5 20 being controlled in dependence upon rotational speed by way of a pressure-control valve 1 7, that is to say, the pressure in the suction chamber increases as the rotational speed increases.

25 A piston of an injection timer 1 8 is acted upon from the suction chamber 5.

A discharge passage 1 9 branches from the suction chamber 5 in the housing 1 and incorporates an overflow valve 20 operating 30 as a constant-flow valve. A throttle valve 21 for influencing the control pressure can be disposed downstream of the overflow valve 20. The function of the overflow valve and of the throttle valve disposed downstream is as 35 follows: the overflow quantity is controlled by the cross section x between the valve spool body and the bore y in dependence upon the hydraulic equilibrium between the pressure times surface area of the front end face of the 40 valve spool and the reduced pressure on the rear end face of the valve spool times the area of the rear end face of the valve spool, plus spring force.

The spring unit 15, opposing the hydraulic 45 force acting upon the piston 14, can comprise one spring or, alternatively, a plurality of springs which cooperate by way of spring abutment plates and which are advantageously arranged so as to act in tandem. In each 50 case, the force of at least one of the springs can be varied by means of a driver member 22 which, in the present instance, is in the form of a piston and is arranged coaxially of the actual adjusting piston in the housing 1 55 and is axially adjustable externally of the pump housing 1 by means of an adjusting lever (not illustrated). After the driver member 22 has been removed, the spring unit 15 can be separated from the adjusting piston 14 and 60 changed in a very simple manner, or various spring units can be used with the same basic design. The adjusting piston 14 has a step 23 whose shoulder acts as a support for a sleeve which has a spring abutment plate 24 and 65 which is slipped onto a thinner portion 25 of

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the adjusting piston 14. The plate of the spring abutment plate cap 24 abuts against the housing 1 at 26. A starting spring 28 is disposed between the bottom 27 of the sleeve 70 and the end face of the portion 25 and, when the pump is stationary with the section chamber pressure relieved, the starting spring pushes the adjusting piston 14, and thus the portion 25, out of the sleeve 24 to a certain 75 extent, whereby the annular valve slide 8 of the injection pump is in turn displaced to such an extent (upwardly as viewed in the Figure) that the mouth of the pressure passage 6 no longer emerges from the annular valve slide 8 80 during the pumping stroke, so that the entire quantity of fuel delivered by the fuel injection pump is injected as a starting quantity. As soon as the internal combustion engine has started, and a certain pressure has been built 85 up in the suction chamber 5 by the feed pump 16, the adjusting piston 14 is displaced against the force of the starting spring 28 until the step 23 strikes against the sleeve 24, which corresponds to full load with respect to 90 the position of the annular valve slide 8.

The idling speed is controlled by an idle-running spring 29 which abuts at one end against the driver member 22 and at the other end against an intermediate spring abutment 95 plate 30 which is mounted on a spring plate bush 31 so as to be axially displaceable in the direction of the force of the spring 29, the spring plate bush 31 being arranged on the sleeve 24 so as to be axially displaceable in 100 the same direction. Freedom of movement in the opposite direction is in each case prevented by a retaining ring 32 arranged on the sleeve 24 or on the spring plate bush 31. A regulating spring 33 acts upon that side of 105 the intermediate spring abutment plate 30 which is remote from the idle-running spring 29, the other end of which regulating spring abuts against the spring plate bush 31. An adaptation spring 34 is disposed between the 110 spring plate bush 31 and the spring abutment plate sleeve 24, the travel of the sleeve 24, that is to say, the change in the force of the adaptation spring 34, being limited by a shoulder 35 in the spring plate bush 31. 11 5 The governor operates in the following manner:

After the engine has been started and the starting spring 28 has been compressed, and provided that the driver member 22 is in its 120 idling position corresponding to the idling speed, the fuel pressure in the suction chamber 5 displaces the adjusting piston 14, together with the spring unit 1 5, upwardly towards the driver member 22, and the annu-125 lar valve slide 8 is displaced to the left until the quantity of fuel injected effects an idling speed which is regulated with a minimum degree of speed drop by a residual amount of travel in the idle-running spring 29. Referring 130 to Fig. 1, the adjusting piston 14 is in its

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position after starting but before it is displaced into the idling position, whereas the driver member 22 has been displaced from the idling position to the left towards the adjust-5 ing piston 14. That is to say, as soon as the adjusting piston 14 and the spring assembly 15 have been displaced upwardly when adequate pressure prevails in the suction chamber 5, idling can no longer be obtained and a 10 quantity of fuel corresponding to part load is injected. As soon as the load on the engine then decreases, the rotational speed increases the thus the pressure in the suction chamber 5, and the adjusting piston 14 displaces the 15 sleeve 24 and the spring plate bush 31 upwardly against the force of the regulating spring 33, thus resulting in a reduction in the quantity of fuel injected. Thus, a different quantity of fuel injected is established accord-20 ing as to the manner in which the driver member 22 is displaced by the accelerator pedal, the spring 33 being compressed after the admissible maximum rotational speed has been exceeded, and a governing-down opera-25 tion is correspondignly effected. Referring to Fig. 1, the spring unit 1 5 is in the position for full load, that is to say, a position which is assumed during operation of the internal combustion engine when it is effected by the 30 driver member 22 by virtue of the latter having been displaced up to the spring abutment plate 30 (full load position). Thus, this governor operates as an idling and maximum speed governor, namely as a governor which 35 regulates the idling speed or the maximum speed. The quantity of fuel injected in the intermediate load positions is determined by the driver of the internal combustion engine. In the illustrated embodiment, the left hand 40 half of the spring plate bush 31 abuts against the housing at 26 when in the full load position, so that the adaptation spring 34 can act over the entire arbitrary range of adjustment, but also during full load in each case. 45 Namely, during full load, even when the spring plate bush 31 abuts against the housing, the cap 24 can cover an amount of adaptation travel before the governing-down operation is effected by compression of the 50 regulating spring 33. In contrast to this, the spring plate bush 31 does not abut against the housing in the right hand half of the illustrated governor, but is held in the illustrated floating position by the adaptation 55 spring 34. However, as soon as the driver member 22 is displaced into the full load position, that is to say, the regulating spring 33 acts directly upon the spring abutment plate 30, the shoulder 35 of the spring plate 60 bush 31 is applied to the flange of the cap 24, the adaptation spring 34 being correspondingly compressed. Thus, adaptation cannot be effected during full load. Matters are different over the entire range of part load in which 65 the spring plate bush 31 assumes the illustrated position relative to the cap 24 or an intermediate position corresponding to the prevailing adaptation. The advantage over the construction of the governor illustrated in the 70 left hand half resides particularly in the fact that adaptation is eliminated along the natural hydraulic full load curve.

The space which accommodates the spring unit 15, and into which the driver member 22 75 enters at one end and the adjusting piston 14 enters at the other end, is pressure-relieved to the suction side of the pump by way of a passage 36. In the governor m accordance with the invention, the principle of equilibrium 80 between hydraulic pressure on the one hand and spring forces on the other hand is optimised by the favourable structural arrangement and the small installation space required. Alternatively, in accordance with the invention, 85 the spring unit 1 5 can be designed such that the governor operates as a variable-speed governor, that is to say, a specific speed of the internal combustion engine corresponds to each position of the driver member 22. 90 In order to obtain satisfactory smooth running of the internal combustion engine when it is cold, it may be necessary to increase the quantity of fuel injected during idling. Provided that the internal combustion engine is 95 cold, such an increase in the idling quantity can be effected by slightly reducing the pressure in the suction chamber 5, whereby the idling-running spring 29 correspondingly maintains the adjusting piston 14 in its down-100 wardly displaced position for a slightly longer period of time, so that the annular valve slide 8 effects the injection of a correspondingly greater quantity of fuel. As is illustrated in Fig. 1, the pressure in the suction chamber 5 105 can be reduced in this manner by discharging a partial quantity. This partial quantity flows through a passage 55 which is controlled by a thermostatic valve 56 and a throttle valve 57 connected in series therewith. The discharge 110 passage 55 opens into the spring chamber 43 which is pressure-relieved by way of the relief passage 36. The throttle valve 57 is set in conformity with the maximum admissible outflow quantity. The thermostatic valve 56 115 operates with an expansible regulator 58 controlled by the engine cooling water which is conducted by way of a passage system 59 to and around the expansible regulator 58. As soon as the temperature of the engine in-120 creases, the expansible regulator 58 causes displacement of the movable valve member 60 and thus reduces or terminates the off-flowing quantity of fuel. When the engine is cold, the quantity of fuel flowing off, that is to 125 say, th additional quantity of fuel injected, decreases uniformly as the temperature rises.

Fig. 2 shows a corresponding device for controlling the quantity of fuel flowing off for the purpose of idling enrichment when the 130 engine is cold, a solenoid valve 61 being

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provided instead of a thermostatic valve 56. The solenoid valve 61 is controlled from the engine, wherein the movable valve member 60' shuts off the discharge passage 55 as 5 soon as the corresponding engine temperature has been attained.

A device, illustrated by way of example in Figs. 1 and 2, for the purpose of idling enrichment when the engine is cold can be 10 combined with a corresponding adjustment of the injection timing. Advantageously the injection timing is adjusted to "advance" when the engine is cold, in order to give the fuel in the combustion chamber sufficient time for 1 5 combustion.

Fig. 3 shows a combination of this kind. Supplementing the arrangement illustrated in Fig. 1, a roller bearing 62 is rotatabiy mounted in the housing 1 of the fuel injection 20 pump and reciprocates a cam plate (not illustrated) which is connected to the pump piston of the injection pump 2. The cam plate is driven directly by the drive shaft of the injection pump for rotation. A pin 63 is connected 25 to the roller ring 62 and is actuated by an injection timing adjusting piston 18'. The fuel flows from the suction chamber 5 by way of a damping throttle 64 and a bore 65, each disposed in the piston 1 8', to the end face 66 30 of the adjusting piston 18' and displaces the latter against the force of a return spring 67. The commencement of the instant of injection is thereby varied in dependence upon the rotational speed. This adjustment is matched 35 to an internal combustion engine operating at a normal temperature. However, in the case of a cold internal combustion engine, the commencement of injection should be advanced in the lower range of speed, in order to give 40 the fuel sufficient time for combustion. In order to obtain this advance of the commencement of injection, a stop lever 68,

which is pivoted at 69 and is adjustable by way of an expansible regulator 70, acts upon 45 that end of the pin 63 which is remote from the roller bearing 62. The expansible regulator 70 is in turn controlled by the engine cooling water which is conducted around the expansible regulator in the chamber 71. The illus-50 trated position of the stop lever 68 corresponds to a hot internal combustion engine, and therefore the injection timing position 18' can assume its initial position. On the other hand, when the engine is cold, the control 55 stud 72 of the expansible regulator 70 is withdrawn, so that the stop lever 68 displaces the pin 63 to the left, which corresponds to advancing the commencement of injection. To ensure that frictional connection exists be-60 tween the stop lever 68 and the control stud 72, the stop lever 68 is acted upon by means of a spring 73 which acts upon the corresponding end of the stop lever 68. That end of the spring 73 which is remote from the 65 lever 68 abuts against a piston 74 which is guided in the housing and which has a central bore 75 for accomodating a valve spool 76. A radial bore 77 communicating with the suction chamber 5 opens into the central bore 75 70 and is controlled by the end face of the valve spool 76. The valve spool 76 is actuated by the stop lever 68 against the force of a return spring 78. According to the temperature of the internal combustion engine, that is to say, 75 according to the position of the valve spool 76, a larger or smaller quantity of fuel flows from the suction chamber 5 into the central bore 75 and then by way of a throttle bore 79 into a pressure-relieved chamber 80 above the 80 piston 74. The piston 74, and thus the control cross section at 82 between the radial bore 77 and the valve spool 76 can be pre-set by means of a set screw 81. By virtue of this design of the invention, the idling speed is 85 increased when the internal combustion engine is cold by reducing the pressure in the suction chamber 5, in the same manner as described in greater detail with reference to the embodiment shown in Fig. 1, and, at the 90 same time, the injection timer is displaced to "advance" when the internal combustion engine is cold, although, by virtue of the reduction of the pressure in the suction chamber 5, a "retard" adjustment is more to be antici-95 pated from the hydraulic adjustment of the injection timer.

In the embodiment illustrated in Fig. 2, an additional possibility of introducing an adjusting variable for load dependence into the 100 control is provided by allowing a portion of the fuel in the suction chamber 5 to flow off in a manner controlled in dependence upon load by controlling the solenoid in dependence upon load. The pressure thereby corre-105 spondingly changes in dependence upon load, thus resulting on the one hand in a corresponding change in the pressure acting upon the adjusting piston 14 and, on the other hand, in a change in the adjusting variable of 110 the piston 18.

Claims

1. A fuel injection pump for an internal combustion engine having an hydraulic speed 115 governor in which an adjusting piston acting upon an injection quantity adjusting member is actuated against spring means by a control pressure of a pressure source supplied at a speed dependent pressure by a feed pump 120 driven at a speed in synchronism with the engine speed, the control pressure being adjustable by means of a valve to effect a change in the injection quantity, the valve being disposed in a passage branching from 125 the pressure source and being controllable by a servo motor, such that the valve is open after the internal combustion engine is cold to lower the control pressure and thereby increase the quantity of fuel injected and the 1 30 valve is closed when the engine is hot.

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2. A fuel injection pump as claimed in claim 1, in which the flow-through cross section of the valve is controlled in dependence upon temperature.

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3. A fuel injection pump as claimed in claim 1 or 2, in which the cooling water of the engine acts as the temperature carrier medium.

4. A fuel injection pump as claimed in any 10 one of the preceding claims, in which the servo motor is electrically operable.

5. A fuel injection pump as claimed in any one of claims 1 to 3, in which an expansible or bimetal element acts as a servo motor of

15 the valve.

6. A fuel injection pump as claimed in any one of the claims 1 to 4, in which a solenoid acts as the servo motor.

7. A fuel injection pump as claimed in any 20 one of the preceding claims, in which an adjustable throttle is additionally disposed in the passage.

8. A fuel injection pump as claimed in any one of the preceding claims, in which the

25 pump is a distributor pump having a reciprocating and simultaneously rotating pump piston, an annular valve slide arranged therear-ound to act as an injection quantity adjusting member which is actuated by way of an 30 intermediate lever by an adjusting piston of the hydraulic governor which is actuated by the speed-dependent fuel pressure against the force of regulating springs, the springs of the governor being disposed in the chamber at 35 the pressure-relieved end of the adjusting piston.

9. A fuel injection pump as claimed in claim 8, in which the passage opens into the pressure-relieved spring chamber.

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10. A fuel injection pump as claimed in any one of the preceding claims, in which the fuel injection pump has a device for timing the instant of injection in dependence upon rotational speed, and that the commencement 45 of injection is adjustable to "advance" when the engine is cold by intervention of the said device, and that the intervention is undertaken by the servo motor.

11. A fuel injection pump as claimed in 50 claim 10, in which the servo motor actuates a movable valve by way of a lever which additionally intervenes in the injection timing.

12. A fuel injection pump constructed and arranged substantially as hereinbefore de-

55 scribed with reference to and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd.—1980.

Published at The Patent Office. 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.